Yahoo!, Google and Microsoft have passed up the chance to take part in a web conference on internet freedom being hosted by human rights group Amnesty International this evening.

The event is being held to discuss how free debate is being quashed by oppressive regimes. The three tech giants could have made a crucial contribution to the debate over whether isolation or inclusion is the best way to help people living under such regimes, as all have been criticised recently for bowing to oppressive practices.